The present invention relates to an engine start/stop system for controlling starting and stopping of a vehicle engine, and more particularly, to an engine start/stop system including an electronic key that communicates with a vehicle.
In addition to improving basic performance and safety, vehicles such as automobiles are now also required to improve operating convenience. Japanese Laid-Open Patent Publication Nos. 2001-289142 and 2001-311333 each describe a system for controlling the starting and stopping of an engine provided with a smart ignition function to improve operating convenience. In such a type of an engine control system, when a user (driver) carrying an electronic key enters the vehicle, the electronic key automatically communicates with a controller, which is arranged in the vehicle. During the communication, the electronic key transmits an ID code to the vehicle. The controller in the vehicle then determines whether the ID code of the electronic key matches an ID code that is unique to the vehicle (smart ID authentication). When the ID code of the electronic key matches the ID code of the vehicle, the controller enables the starting and stopping of the engine. The user then operates a push button, which is located in the passenger compartment, to start or stop the engine. In other words, the user may start or stop the engine just by entering the vehicle and operating the push button.
In the above engine control system, the smart ID authentication is not performed when, for example, the battery of the electronic key is drained or when a communication anomaly occurs. To cope with such problems, the engine control system performs transponder ID authentication instead of smart ID authentication. More specifically, the electronic key includes a transponder. When the user inserts the electronic key into a key socket located in the instrument panel, induced electromotive force is generated in the transponder. The transponder uses the induced electromotive force to transmit a transponder signal, which includes a transponder code, to the controller in the vehicle. The controller then determines whether the transponder code of the electronic key matches a transponder code that is unique to the vehicle (transponder ID authentication). When the transponder code of the electronic key matches the transponder code of the vehicle, the controller enables the starting of the engine and validates the operation of the push button.
In the prior art system described above, when transponder ID authentication is performed, an interlock device interlocks the electronic key so that it cannot be removed from the key socket. However, when smart ID authentication is performed, the interlock device does not interlock the electronic key even when the user inserts the electronic key in the key socket for one reason or another. Thus, the user can remove the electronic key from the socket. In this manner, the electronic key is removable from the key socket in some cases and not removable from the key socket in other cases. This may result in the user erroneously determining that the system is not functioning properly.